Cockcroft-Gault revisited: New de-liver-ance on recommendations for use in cirrhosis

Table 1 Different methods of estimating creatinine-clearance (A): Equations I-IV were evaluated in the original Cockcroft-Gault study, Equation V is a modified Cockcroft-Gault that only incorporates age and serum creatinine into the equation; B: Different body weight equations tested in the Cockcroft-Gault equation to compensate for various body types

A: Formula = CrCl (mL/min)		B: Formula = weight (kg)
I1	[(140 - age)(weight in kg)] (72 × SCr)	IBWmale	50 + (2.3 kg × inches > 60)
II	(100/SCr) - 12	IBWfemale	45.5 + (2.3 kg × inches > 60)
III	98 - 16 × [(age - 20)/20] SCr	AdjBW	IBW + [(TBW - IBW) × C2]
IV	(94.3/SCr) - 1.8	LBWmale	9270 × TBW 6680 + (216 × BMI)
V	(140 - age) SCr	LBWfemale	9270 × TBW
VI	100 SCr	FFW	Calculated using BIA[15]

¹CrCl × (1.73 m²/BSA) to normalize to body surface area (BSA) of 1.73 m²;

²0.3 for 30% ABW and 0.4 for 40% ABW. AdjBW: Adjusted body weight; BMI: Body mass index; CrCl: Creatinine clearance; FFW: Fat free weight; IBW: Ideal body weight; LBW: Lean body weight; SCr: Serum creatinine; TBW: Total body weight; BIA: Bioelectrical impedance analysis.

Table 2 Estimating creatinine clearance in morbidly obese patients by Demirovic et al[15] showed that using fat free weight and lean body weight provided the closest estimate to the control 24-h urine creatinine clearance

Method1	Mean estimated CrCl ± SD	Mean bias (mL/min)	± 30% of measured CrCl	± 50% of measured CrCl
Measured CrCl	109.5 ± 44.4
ActBW	217 ± 113	-107	13%	30%
IBW	85 ± 29	+24	48%	89%
AdjBW0.3	129 ± 55	-20	54%	76%
AdjBW0.4	142 ± 63	-33	52%	67%
FFW	103 ± 48	+7	61%	83%
LBW	102 ± 43	+8	56%	87%
MDRD4	96.3 ± 29.4	+13.3	51.90%	87%
Salazar-Corcoran	155.2 ± 65.1	-45.7	46.20%	55.60%

¹All weight variables used in CG equation only. MDRD4[18]: 186 × SCr^-1.154× age^-0.203× (0.742 if female) × (1.210 if black); Salazar-Corcoran[19]: Male: (137 - age) × [(0.285 × Wt) + (12.1 × height meters)²], 51 × SCr; Female: (146 - age) × [(0.287 × Wt) + (9.74 × height meters)²], 60 × SCr; ActBW: Actual body weight; AdjBW_0.3: 30% adjusted body weight; AdjBW_0.4: 40% adjusted body weight; CG: Cockcroft-Gault; CrCl: Creatinine clearance; FFW: Fat free weight; IBW: Ideal body weight; LBW: Lean body weight; MDRD: Modification of diet in renal disease study equation; SD: Standard deviation; Wt: Weight.

Table 3 Results from Dooley et al[21] illustrated that rounding of serum creatinine to 0.6 mg/dL underestimated creatinine clearance by 7%; of note, the majority of clinicians round low serum creatinine values to 0.8 or 1.0 mg/dL

		Mean ± SD (mL/min)	Range (mL/min)	Mean % error	P value
DTPA	All	111 ± 46	45-256
	≤ 100 mL/min	77 ± 14	45-96
	> 100 mL/min	140 ± 45	103-256
CG (no rounding)	All	117 ± 38	55-207	12.9	0.352
	≤ 100 mL/min	98 ± 28	55-152	29.2	0.024
	> 100 mL/min	135 ± 38	86-207	-0.1	0.631
CG (rounding SCr to 0.6 mg/dL)	All	97 ± 30	46-172	-7.0	0.029
	≤ 100 mL/min	82 ± 23	46-127	7.9	0.543
	> 100 mL/min	110 ± 29	72-172	-18.9	0.003

CG: Cockcroft-Gault; DTPA: Diethyl triamine penta-acetic acid; SCr: Serum creatinine.

Table 4 Results from Smythe et al[22] showed that rounding of serum creatinine to 1.0 in elderly patients was less accurate than using the patients actual serum creatinine

Method	Bias = CrClmeas - CrClcalc (CI)	Precision
CG using IBW without gender adjustment
Actual SCr	2.3 (-10.3-14.8)	22.5
Rounded SCr	28.8 (19.1-38.4)	17.4
CG using ActBW without gender adjustment
Actual SCr	-13.6 [-26.8-(-0.43)]	23.6
Rounded SCr	16.3 (4.5-28.1)	21.2
CG using ActBW with gender adjustment
Actual SCr	-5.2 (-17.2-7.1)	22.1
Rounded SCr	22.6 (11.5-33.7)	19.9

ActBW: Actual body weight; CG: Cockcroft-Gault; CrCl: Creatinine clearance; IBW: Ideal body weight; SCr: Serum creatinine.